1. Field of the Invention
This invention relates to an automatic drip coffeemaker, and more particularly to an improved heating and control means for starting a brewing cycle at a pre-set time and for maintaining the brewed coffee at a suitable serving temperature for an indefinite period of time after it has been brewed.
2. Description of the Prior Art
Drip brewing apparatus for coffee is well known. A molded plastic housing is conventionally provided with a horizontal base for holding a receptacle such as a glass carafe. A generally vertical wall is integrally molded with the base and is provided with an overhanging top wall located above the carafe for holding a coffee brew basket. The basket is filled with dry ground coffee and then positioned on the underside of the top wall of the housing. A water reservoir is provided in the generally vertical wall and an electric heater is positioned in the plastic base below the carafe for delivering heated water through an opening in the top wall of the housing and into the coffee brew basket. The heated water flows through the grounds and brewed coffee drips into the carafe receptacle. The base mounted heater performs a dual function in supplying the pumping action to move the water through its cycle as well as keeping the brewed coffee hot.
It is common practice to provide a thermostatic switch in heat exchange relation with a water tube of the heater for both sensing the temperature of the water in the tube and the temperature of the brewed coffee in the carafe that is positioned on the base above the heater.
In a prior U.S. Pat. No. 4,069,750 to Kemp dated Jan. 24, 1978 an analog timer with gears and levers is provided for automatically closing a switch to start operation of the coffeemaker at a pre-set brew time, and maintaining the coffee warm after it has been brewed. A manually operable lever 40 of an ON OFF AUTO switch is provided to terminate the keep warm cycle of the coffeemaker.
Low cost digital LED clock modules are available for use as clock radio timers and appliance timers. A prior digital LED clock module, manufactured by National Semiconductor Corporation, and identified as MA1010/1042/1043 Series is such a timer, which has been particularly designed as a clock radio timer and is also available for use as an appliance timer. However, the output signals from the timer are not directly usable for controlling a drip coffeemaker since one signal SLEEP OUTPUT is removed after 59 minutes, which may be shorter than a desired coffee keep warm time, and the usual ALARM OUTPUT signal for actuating an alarm clock radio is an oscillating signal for driving a speaker. Thus, it is not readily usuable actuating a control circuit for a coffeemaker, wherein a steady state direct current signal is desired.